1. Field of the Invention
The present invention generally relates to a roll core holding device for a rolled thin plate shape article. More particularly, the present invention relates to a roll core holding device equipped with a roll core release mechanism which automatically and reliably releases the empty roll core; i.e., a rolled article that has been wholly used, from a rotary printing machine.
2. Description of the Prior Art
Conventional roll core holding devices have been disclosed in Japanese Patent Publication No. 51-18842 entitled "Automatic Paper Roll Changing Device in a Rotary Printing Device" (hereinafter "Automatic") and Japanese Patent Publication for Utility Model No. 47-29900 entitled "Unwinding Drum" (hereinafter "Unwinding").
A paper roll holding section, disclosed in "Automatic" is shown in FIG. 9. A paper roll 331 is held by means of a center collar 332 having a taper which is forcibly engaged within a core of the paper roll.
FIG. 10 is sectional view showing one example of mandril type unwinding drum for a strip coil as disclosed in "Unwinding". This unwinding drum comprises a drum segment 441 provided with a protruding member 443 and a side guide 442 formed with a groove. This protruding member 443 is so arranged as to coincide with the same surface level of the side guide 442. The groove of the side guide 442 is defined by assembling the protruding member 443 with the side guide 442. The drum segment 441 and the protruding member 443 are forcibly opened or moved in the radius direction as a wedge shaped member 444 is moved forward.
In a printing process using a rotary printing machine, a printing web fed from a paper roll is subjected to a predetermined tension caused by restraining force applied to the paper roll. This restraining force is typically generated by forcibly pressing belt on the external surface of this paper roll. Since this procedure may often injure the paper surface, a shaft for holding the paper roll applied with the restraining force has recently been proposed. This new procedure requires fixing the paper roll with the holding member firmly so as to preventing the engaged members from loosening.
The arrangement shown in FIG. 9 requires a relatively large force to press the tapered center collar in order to prevent the engaged section from slipping under the influence of the restraining force. Although the arrangement shown in FIG. 10 can provide a firm engagement, a new problem may occur when the empty core of paper roll is disengaged from the roll holding member. The spring force and the weight of the empty core are too small to disengage the holding member from the core, so that this may sometimes cause the empty core to interfere with the printing device.